1. Field of the Invention
The invention relates to a proportioner as well as a fluid proportioning system.
2. Description of the Related Art
In FR-A-852,681 a two conduit proportioning system is described in which one conduit acts to effect the pump stroke of the proportioner whilst the other conduit carries the fluid to be proportioned and also acts to control the return movement of the piston in the proportioner.
According to a specific embodiment of this French patent specification the fluids used in both conduits can be the same. This means that the fluid which effects compression can be the same kind of grease as the fluid which is used for greasing. The fluid for the working stroke of the piston is not refreshed and subjected to severe loading. If this fluid is oil there is no problem, but if one aims to use the same fluid, i.e. grease for both conduits, deterioration of the grease may result. Finally grease will decompose into seep.
In the prior art, fluid proportioning systems are used where a constant quantity of fluid has to be dispensed in a centrally controlled manner at quite a large number of places, always to some extent independently of the feed pressure. One example of this is grease lubricating systems of the type used in vehicles. It is important here that a quantity of grease should always be fed to a different number of bearing points after a certain time, or after, for example, a number of brake applications. A greater or smaller quantity of grease may be required, depending on the bearing. For such accurate proportioning, use is made of proportioners in which a piston moves to and fro. The volume displaced by such a piston determines the quantity of proportioned grease. Such a piston is moved in one direction through the build-up of pressure, and the return movement is achieved by means of a spring. With such a system it is possible to grease a large number or a small number of lubrication points by means of one system. This is important in particular in body-building, because with a single universal system, various vehicles can be provided with a different number of lubrication points. In recent years attempts have been made to use ever thicker lubricating grease. The advantage of this is that it runs out of the bearing less quickly, and it seals the bearing better relative to the environment, with the result that a lower grease consumption can be achieved. Apart from the cost aspect, environmental considerations play an important role. In the case of the currently used lubricating systems so-called "0-grease" or the more free-flowing "00-grease" are used, while efforts are being made to use 1-grease or 2-grease. If such a thick grease is used, problems occur through the fact that the return of the piston to the proportioner housing under the influence of the spring used is no longer guaranteed. As soon as this return can no longer be guaranteed, lubrication at the next stroke can no longer be guaranteed either. In the case of thick grease, problems occur in particular where there are long and/or thin lines, and at a lower temperature. A solution proposed in the prior art is to operate the various proportioners in succession. For this purpose, a complex system which controls the operation in succession of said proportioners is necessary. Working with a ring line has also been proposed. All such systems are satisfactory in certain applications, but it is not possible to extend or reduce such a system in a flexible way.